The invention relates generally to internal combustion piston engines, fluid pumps and similar machines and, more particularly to a Double-Acting Scotch Assembly (DASY) for an X-Engine configuration.
The most widely used engine configurations in use today are in-line, “V” and horizontally-opposed or ‘flat’. Almost all of these engines use conventional connecting rods (“con rods”) in the power conversion system. Con rods, due to the nature of their motion, produce multiple orders of vibration such that there is no practical way to cancel out all of the resultant vibration in an engine that has con rods. Some conventional engine configurations which use con rods, such as the 90° V-8, have balance for 1st-order and 2nd-order vibrations, but practically all engines with conventional con rods are never balanced for 3rd-orders and above.
The Scotch yoke is a mechanism for converting the linear motion of a slider into rotational motion or vice-versa. The piston or other reciprocating part is directly coupled to a sliding yoke with a slot that engages a pin on the rotating part. A bearing block interfaces the rotating motion at the crankshaft with the sliding linear motion at the yoke. The shape of the motion of the piston is a pure sine wave over time given a constant rotational speed.
Unlike conventional engine configurations in use today, the scotch yoke mechanism is a mechanism that couples the reciprocating pistons to the rotating crankshaft with true harmonic motion for the reciprocating mass such that an engine that uses scotch yokes can be said to be “100% balanced for all orders” if it is balanced for 1st-order forces and moments.
With regards to reducing friction in an engine, the scotch yoke mechanism can be used in a double-ended or “double-acting” fashion such that each reciprocating assembly has a piston at either end so each crank pin bearing on the crankshaft is coupled to two pistons instead of just a single piston. In this way, the ratio of total engine bearings/cylinders is therefore reduced and the crankshaft is shorter and lighter for a given number of cylinders. A further benefit of the double-acting scotch yoke is that the fluid motion inside the crankcase is minimized because opposite pistons simply push air in between them, whereas in “V”-type engines and in-line engines there is a larger mass of air which is pushed around the engine's bulkheads in a way that causes larger amounts of fluid friction.